Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $219.98   5.708%   $232.5365   $232.54   $232.55   $232.50  
  Purchase #2 $46.49   5.372%   $48.9874   $48.99   $49.00   $49.00  
  Purchase #3 $186.87   4.839%   $195.9126   $195.91   $195.90   $195.90  
  Purchase #4 $58.43   3.857%   $60.6836   $60.68   $60.70   $60.70  
  Purchase #5 $226.29   10.559%   $250.184   $250.18   $250.20   $250.20  
  Purchase #6 $226.85   6.253%   $241.0349   $241.03   $241.05   $241.00  
  Purchase #7 $157.74   10.810%   $174.7917   $174.79   $174.80   $174.80  
  7 purchase totals = $1,122.65       $1,204.1307   $1,204.12   $1,204.20   $1,204.10